Excellent laccase mimic activity of bimetallic Cu, Bi-PTs nanozyme sensor and its applications in quantification of morphine

Nanozymes have been valuable tools in colorimetric analysis due to their ease of production, long-term stability, and adaptable enzymatic activity, enabling them to induce color changes in substrates. This study presents a straightforward enzyme-based colorimetric sensor for morphine ( MOR ) detection. The sensor utilized the laccase-like activity of a self-synthesized Cu, Bi-phosphotungstic acid ( Cu, Bi-PTs ) nanozyme, which was loaded with phosphotungstic acid, copper, and bismuth through a one-pot microwave method. This nanozyme was capable of catalyzing the coupling reaction of 2,4-dichlorophenol ( 2,4-DP ) and 4-aminoantipyrine ( 4-AP ), leading to the conversion of colorless phenolic compounds into red-colored products. The method demonstrated a detection limit of 1.88 μg/mL for MOR and a linear dynamic range from 3.333 to 400 μg/mL. The calibration curve, given by the equation y = 0.0015x + 0.4081, exhibited excellent linearity (R 2  = 0.9914), confirming the method's reliability for quantitative analysis. The developed colorimetric method was successfully applied to real samples, showing relative standard deviations (RSD) between 1.4 and 4.3% for MOR detection. These results demonstrated that the method was sensitive, cost-effective, and rapid, making it suitable for the efficient determination of MOR .